The inhalation of oxygen enriched air is sometimes prescribed for treatment of certain chronic breathing disorders, such as chronic obstructive pulmonary disease and emphysema. The traditional methods for generating oxygen enriched air for such treatment generally utilize stationary equipment to manufacture oxygen chemically, e.g. by electrolysis or pressure swing adsorption, or to refine oxygen from air cryogenically. Stationary sources of oxygen enriched air are unsuitable for many patients because the roaming range of the user is limited to the immediate vicinity of the enriched air supply.
Oxygen produced by a stationary source can be stored in tanks and carried by the patient to be consumed away from the source. However, oxygen is usually stored under pressure to maximize storage capacity. Storage tanks capable of holding compressed gas are normally bulky and heavy. Patients who suffer from breathing difficulty are likely to be weak and generally are not able to easily handle heavy compressed oxygen tanks. Furthermore, tank capacity normally limits usage to at most about a couple of hours away from the primary source of oxygen enriched air.
Membrane separation technology would seem to show promise for portable generation of oxygen enriched air. Oxygen in ambient air contacted with an oxygen selectively permeable membrane will preferentially permeate through the membrane to form an oxygen rich permeate fraction and an oxygen depleted, nitrogen rich retentate fraction. However, conventional enriched air delivery apparatus use membrane materials which have inadequate flux to provide enough enriched breathing air in a small unit. Also, accessory equipment such as fans and valves are utilized to permit the apparatus to function properly. Despite the advent of membrane separation technology, a compact, light weight, effective air flow capacity yet fully mobile, portable oxygen enriched air generator has been unavailable.
U.S. Pat. No. 4,632,677 describes a high humidity oxygen enricher that includes an array of membrane cells each of which is selectively permeable to permit oxygen and water vapor to permeate into chambers of the cell at a greater rate than nitrogen. The membranes are formed of silicone rubber, polymethylpentene, silicone-polycarbonate copolymer and polyphenylene ethers, for example. The figures show that wheels are utilized to move the apparatus about. The apparatus also uses an external source of electric power connected by a cable and thus is not portable. These observations imply that the bulk and weight of this oxygen enricher are substantial.
Certain amorphous copolymers of perfluoro-2,2-dimethyl-1,3-dioxole ("PDD") have recently been found to be suitable for making a membrane capable of separating air to form oxygen enriched air at high flux. Such membranes are disclosed in U.S. Pat. No. 5,051,114 which is incorporated in its entirety by reference herein.
The ability to fabricate a membrane having a very thin coating of PDD copolymer on a microporous substrate of extremely high surface-to-volume ratio such as hollow fibers was recently developed. It has now been discovered that membrane modules having multiple, PDD copolymer thinly coated hollow fiber membranes can be used to make a truly portable, oxygen enriched air supply apparatus. High oxygen flux allows the module to be small enough that adequate amounts of oxygen enriched air can be generated by processing very low volumetric rates of ambient air. Consequently, auxiliary components such as fans, pumps, tubes, valves and batteries are commensurately small and provide a portable apparatus light weight and small enough to be carried by many weak or infirm patients.
Accordingly, there is now provided an oxygen enriched air supply apparatus comprising
a membrane separation module comprising an oxygen gas selectively permeable membrane defining within the module a retentate chamber on one side of the membrane and a permeate chamber on the opposite side of the membrane; PA1 an ambient air intake fan having an exhaust port in fluid communication with the retentate chamber; PA1 a vacuum pump having a suction port and a discharge port, the suction port being in fluid communication with the permeate chamber; PA1 gas reservoir means for storing oxygen enriched air received from the discharge port; PA1 breathing nozzle means for delivering oxygen enriched air to an animal; PA1 a gas transfer tube extending from the reservoir means to the breathing nozzle means; and PA1 power supply means for providing electrical power to operate the portable oxygen enriched air supply apparatus. PA1 a membrane separation module comprising an oxygen gas selectively permeable membrane defining within the module a retentate chamber on one side of the membrane and a permeate chamber on the opposite side of the membrane; PA1 an ambient air intake fan having an exhaust port in fluid communication with the retentate chamber; PA1 a vacuum pump having a suction port and a discharge port, the suction port being in fluid communication with the permeate chamber; PA1 gas reservoir means for storing oxygen enriched air received from the discharge port; PA1 breathing nozzle means for delivering oxygen enriched air to an animal; PA1 a gas transfer tube extending from the reservoir means to the breathing nozzle means; and PA1 a membrane separation module comprising an oxygen gas selectively permeable membrane defining within the module a retentate chamber on one side of the membrane and a permeate chamber on the opposite side of the membrane; PA1 an ambient air intake fan having an exhaust port in fluid communication with the retentate chamber; PA1 a vacuum pump having a suction port and a discharge port, the suction port being in fluid communication with the permeate chamber; PA1 breathing nozzle means for delivering oxygen enriched air to an animal; PA1 a gas transfer tube extending from the discharge port to the breathing nozzle means; PA1 a conserver valve in the gas transfer tube; PA1 sensor means in the gas transfer tube downstream of the conserver valve for detecting the start of inhalation by the animal; and PA1 control means for operating the conserver valve to be open only for a preselected duration after start of inhalation by the animal.
There is also provided a process comprising the step of using an apparatus to produce oxygen enriched air, the apparatus comprising
power supply means for providing electrical power to operate the oxygen enriched air supply apparatus.
This invention further provides an oxygen enriched air supply apparatus comprising